Potassium carbonate

Production

Potassium carbonate is prepared commercially by the reaction potassium hydroxide with carbon dioxide:

2 KOH + CO₂ → K₂CO₃ + H₂O

From the solution crystallizes the sesquihydrate K₂CO₃·​³⁄₂H₂O (“potash hydrate”). Heating this solid above 200 °C gives the anhydrous salt. Alternative method, potassium chloride is treated with carbon dioxide in the presence of an organic amine to give potassium bicarbonate, which is then calcined:

2 KHCO₃ → K₂CO₃ + H₂O + CO₂

Applications

• (historically) for soap, glass, and china production
• as a mild drying agent where other drying agents, such as calcium chloride and magnesium sulfate, may be incompatible. It is not suitable for acidic compounds, but can be useful for drying an organic phase if one has a small amount of acidic impurity. It may also be used to dry some ketones, alcohols, and amines prior to distillation.
• in cuisine, where it has many traditional uses. It is an ingredient in the production of grass jelly, a food consumed in Chinese and Southeast Asian cuisines, as well as Chinese hand-pulled noodles and moon cake. It is also used to tenderize tripe. German gingerbread recipes often use potassium carbonate as a baking agent, although in combination with hartshorn. Use of potassium carbonate must be limited to a certain amount to prevent harm, and should not be used without guidance.
• in the alkalization of cocoa powder to produce Dutch process chocolate by balancing the pH (i.e., reduce the acidity) of natural cocoa beans; it also enhances aroma. The process of adding potassium carbonate to cocoa powder is usually called “Dutching” (and the products referred to as Dutch-processed cocoa powder), as the process was first developed in 1828 by Dutchman Coenraad Johannes van Houten.
• as a buffering agent in the production of mead or wine.
• in antique documents, it is reported to have been used to soften hard water.
• as a fire suppressant in extinguishing deep-fat fryers and various other B class-related fires.
• in condensed aerosol fire suppression, although as the byproduct of potassium nitrate.
• as an ingredient in welding fluxes, and in the flux coating on arc-welding rods.
• as an animal feed ingredient to satisfy the potassium requirements of farmed animals such as broiler breeders.
• as an acidity regulator in Swedish snus